The DOC model of microemulsions: microstructure, scattering, conductivity and phase limits imposed by sterical constraints (original) (raw)

1997, Colloids and Surfaces A: Physicochemical and Engineering Aspects

Using a Voronoi cell tessellation of space, a complete set of microstructure approximations with a local morphology that evolves continuously from isolated spheres to disordered lamellae via connected cylinders has been introduced by Barry Ninham and co-workers to describe microemulsions. For 10 years, this continuous microstructural change has been observed in a large number of microemulsion and copolymer systems. In the case of stiff interfaces, where bending energy damps local curvature fluctuations, three constraints that govern microstructures have to be fulfilled simultaneously: the imposed volume fraction; the specific oil-water interface; and the minimum elastic energy, with negligible entropic contributions. From this model, simple analytic expressions are able to predict the characteristic size D* and the connectivity Z of the microstructure at any composition, when the surfactant parameter p can be derived from the phase diagram shape. Once D* and Z are known, the conductivity, scattering peak position as well as phase boundary can be predicted from the spontaneous curvature alone. The model is known as the disordered open connected model (DOC) and is still the only model proposed for microemulsions compatible with nonmonotonic behaviour of the electric conductivity with water volume fraction. © 1997 Elsevier Science B.V.

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